Field of the Invention
The present invention relates to a light emitting device and an image forming apparatus.
Discussion of the Background
Light emitting devices that include a light guide member to guide light from a light source are used in various applications such as an illuminating device, a display device, and a backlight of a liquid crystal display. In recent years, light emitting diodes (LEDs) have been widely used to achieve lower power consumption and a smaller device size. Light emitting devices, particularly those using LEDs as the light source, include a light guide member to achieve surface light emission with the LEDs as point light sources. Such a light emitting device, including the light guide member, includes a direct light emitting device and a side light emitting device (see Japanese Unexamined Patent Application Publication No. 2012-138345). In the direct light emitting device, the light source is disposed directly beneath an opposing surface of a light-emitting surface of the light guide member. In the side light emitting device, the light source is disposed on a side of a side surface adjacent to the light-emitting surface of the light guiding member. The side light emitting device can be made smaller in thickness than the thickness of the direct light emitting device, and thus is used for various display devices and illumination devices to achieve smaller device size.
As shown in FIG. 10, a conventional light emitting device includes a light source 200, a light guide plate 300, a diffusion sheet 400, and a display lens 500. The light source 200 is provided with a plurality of LEDs 201. The light guide plate 300 receives, on its side surface, irradiation light from the light source 200. The diffusion sheet 400 diffuses the light guided by the light guide plate 300. The display lens 500 focuses the light diffused by the diffusion sheet 400 onto a display area. In the conventional light emitting device, the light guide plate 300, the diffusion sheet 400, and the display lens 500 are in close contact with each other. Thus, when during fabrication of the light emitting device a foreign object such as dust enters between the light guide plate 300 and the diffusion sheet 400, or between the diffusion sheet 400 and the display lens 500, the foreign object come into pressure contact between the components. Specifically, the foreign object might be encapsulated between the light guide plate 300 and the diffusion sheet 400 or between the diffusion sheet 400 and the display lens 500, due to the entrance of the foreign object during the fabrication, and the like.
When the foreign object is in pressure contact between the light guide plate 300 and the diffusion sheet 400, or between the diffusion sheet 400 and the display lens 500, the light is guided through a portion including the foreign object. Thus, even when the LED 201, which irradiates the portion including the foreign object with light, is not lit in the light source 200, the light might be guided by the portion including the foreign object. As a result, the light might be emitted from an area out of the luminescent display range in the display lens 500. Thus, when the conventional light emitting device is used as a state display device that indicates the state of an apparatus with a display pattern for example, light might be emitted in a way unintended with the display pattern, due to the foreign object included, thereby degrading the display quality.
In view of such a problem, an object of the present invention is to provide a light emitting device that eliminates or minimizes the degradation of the light emitting quality due to the foreign object included, and an image forming apparatus including the light emitting device.